This invention relates generally to radio frequency (RF) circuitry and, more particularly to interconnection and packaging of monolithic microwave integrated circuit (MMIC) chips. There are certain applications of MMICs that are required to handle RF signals having a very wide bandwidth. For example, electronic circuits that interface with photonic communications systems can advantageously employ MMICs for amplifiers, data buffers and similar devices. Some MMICs have a thickness in the range of 2-4 mil (approximately 50-100 μm). Interconnection between MMICs or from MMICs to external components is typically handled by transmission lines formed on substrates that are approximately 10-25 mil (250-625 μm) in thickness, since thinner substrates would be much too brittle to be of practical value.
Therefore, a common packaging problem in many MMIC applications is to provide interconnecting RF transmission lines between MMICs that are 50-100 μm thick and substrates of a much greater thickness, such as 250-625 μm. One solution of the prior art is to employ ribbon interconnects that are up to 30 mil (750 μm) long, but this type of interconnect has a significant effect on bandwidth, output power and noise generated in an interconnected MMIC system. Accordingly, there is a need for an alternative solution for interconnecting MMICs with other MMICs and with external components installed on a common substrate. The present invention is directed to this need.